Experiments are proposed to characterize natural-abundance 15N chemical shifts of alkaloids, antibiotics, and related model compounds for purposes of correlation with structure and to establish a data base for possible relationship with biochemical or pharmacological behavior. The pulsed Fourier transform nmr technique will be used. Molecules chosen include members of the Rauwolfia, Aspidosperma, Lupine, and Cinchana alkaloid families, and monocyclic beta-lactams. Nitrogen chemical shifts of small aromatic molecules will be further characterized and correlated with theoretical models. Ureas, amides, and barbituric acids will be characterized, expecially as tests of a recently proposed model for the influence of lone-pair delocalization on nitrogen shifts. The general methodology will be applied to solution of problems in pharmacological structure.